Equipment for precision positioning or measurement to dimensions in the order of 0.0001 inches or centimeters to 0.00005 inches or centimeters is ordinarily not found in machine shops and production facilities. To achieve this level of tolerances, special quality equipment is required with temperature control of all components including the measuring devices. Typically, only equipment with lower tolerances or old and worn equipment is available.
For example, a conventional grinding machine is provided with a movable platform or work holder that slides on ways in order to vary the distance between the workpiece mounted on the work holder and the grinding wheel or other working tool. The translation or sliding movement of the work holder is achieved by a rotating lead screw or hydraulic cylinder. If the diameter of the workpiece is to be reduced by 0.0001 inches or centimeters, the corresponding in-feed movement or positioning of the workpiece must be 0.00005 inches or centimeters, an increment of distance one half as much as the amount that the diameter is to be reduced. To achieve such accuracy and control of tolerances with the conventional or older worn machinery is next to impossible. This degree of accuracy is particularly difficult to achieve if production is involved where one piece after another must be processed.
A conventional grinding machine 10 is illustrated by way of example in FIG. 1. A workpiece 14 to be machined is mounted for rotation between the centers 15 on the rotating axis 20 driven by motor 18. The centers 15 are secured to a translating platform 12 by bolts 16. The platform 12 translates or slides in ways, not shown, and is mounted on threaded sleeve 22 which translates back and forth driven or inspired by the threads of lead screw 24. Lead screw 24 is mounted for rotation within the bearings 26 by means of a handle 25 and manual grip 25A. The manually operated translating platform assembly is in turn mounted on the base 28 of the grinding machine. An extending arm 34 of the machine base 28 supports the grinding wheel 30 or other working tool for rotation on axis 32 driven by motor 35 via belt 36. Due to the limited tolerances of the threaded lead screw 24, sleeve 22, and sliding ways, of work holder platform 12, the dimensional tolerance in placement of the workpiece 14 relative to the working tool 30 is also limited. More generally, the lower cost or worn equipment ordinarily available for placement and positioning of objects for application in work holders, work stations, manipulators, etc., or for motional response sensing and measurement of parameters is limited.